A network element such as a router, typically comprises one or more line cards each having a number of physical communication ports for connection to network links for carrying communication traffic, and a control card for controlling and managing operation of the line card(s). A number of logical interfaces can be implemented at each physical port for logical connection to other network nodes such as hosts or routers. Each logical interface is defined by a series of parameters which identify the interface and determine its operation in handling traffic. For example, an IPv6 (Internet Protocol Version 6) logical interface typically includes a link local address and one or more global addresses and may also include one or more multi-cast addresses. Other definitions include the transport protocol of the interface, for example, ATM (asynchronous transfer mode), Ethernet, POS (Packet-over-SONET), the bandwidth of the interface and the maximum transmission unit (MTU), i.e. the maximum packet size in octets that can be conveyed in one piece over a link.
In addition to these parameters, each interface is adapted to exchange specific communications with neighboring network nodes for neighbor discovery, in order to identify itself to its neighbors, provide other information to its neighbors to enable its neighbors to configure themselves for communication with the interface, and so that the interface can maintain and update records of its neighboring nodes. Variables and their settings which govern neighbor discovery of an interface are also included in the interface definition.
In Internet Protocol Version 6 (IPv6), communications used in neighbor discovery include router advertisements, router solicitations, neighbor solicitations and neighbor advertisements. A router advertisement is used by routers to advertise their presence, together with various link and internet parameters either periodically, or in response to a router solicitation message. Parameters controlling the frequency at which unsolicited router advertisements are sent, as well as their format are all specified in the interface definition. Parameters governing the frequency of router advertisements typically include minimum and maximum router advertisement intervals. Information contained in router advertisements, which is typically specified as settings of various variables or parameters, include a “managed address configuration flag” which is used by a host for address configuration, “other configuration flag” which is used by a host to configure other (i.e. non-address) information, variables which are used for neighbor unreachability detection, a variable indicating hop limit, and other parameters. Router advertisement messages may also contain internet parameters such as the hop limit that hosts should use in outgoing packets, and optionally, link parameters such as the link MTU. Router advertisements also contain a list of prefixes used by nodes for on-link determination and/or autonomous address configuration, together with flags associated with the prefixes which specify the intended uses of a particular prefix. The advertised on-link prefixes are used by hosts to create and maintain a list for use in deciding when a packet's destination is on-link or beyond a router. Variables and flags which may be associated with each prefix include an on-link flag, an autonomous flag, valid and preferred lifetime values, valid and preferred lifetime decrement flags and an advertisement of prefix flag.
Referring to FIG. 1, which shows a schematic diagram of an example of a network element 101, a definiton of each logical interface 1, 2, 3, 4, 5 . . . etc., is stored in the memory 103, 105 of the associated line card 107, 109 which implements the interface. A copy of each interface definition is also stored in a non-volatile memory 111 of the control card 113, so that a permanent record of the interface definitions are available locally for transferring to a respective line card, if the line card interface definitions are lost, for example, through removal of electrical power to the line card, or for downloading into and initiating a new line card. As shown in FIG. 1, each interface definition includes both a list of settings for neighbor discovery interface parameters and neighbor discovery prefix parameters, which, for example, are used in generating router advertisements.
IPv6 interfaces on routers may be configured using default settings for each neighbor discovery configuration item or parameter. If an operator wishes to use different settings for a particular deployment, the operator is required to modify the settings away from the default values manually for each customer interface. As noted above, each neighbor discovery interface definition includes a large number of parameters whose settings can be specified by an operator. In addition, many thousands, e.g. tens or hundreds of thousands of interfaces may be provisioned on a single router and large amounts of storage space are required to store the IPv6 neighbor discovery interface and prefix parameters against each interface. Furthermore, any changes to neighbor discovery configuration items may need to be made for large numbers of interfaces which is both laborious and time consuming.